[Tfug] CMP *in* ductwork?

[Bexley Hall]

Hi Adrian,

--- On Tue, 9/11/12, Adrian <choprboy at dakotacom.net> wrote:

> So yes, with very few exceptions (namely something directly
> associated with 
> the air handling system, i.e. an airflow sensor, or
> perpendicular crossings 
> of a duct), you can not install any type of cable within an
> "air duct". You 
> can install properly rated cables within an air handling
> space, a plenum, but 
> not within a dedicated ducts.

OK, so why the different attitude towards "air handling spaces"
(which effectively *act* like ducts) vs. actual ducts?  E.g.,
smoke, toxic outgases, etc. will propagate just as effectively in
an air handling space (no distinction is made regarding whether
it is a supply or return path).  And, I can imagine cable (of
any sort) would be more likely to act as a propagating element
(even if it does self extinguish) when it is in the presence of
other building materials that might be present in the air
handling space but would obviously be absent from a "sterile"
duct?

And, how do the single family, single floor residential exceptions
apply?

Aren't standards wonderful (can you spell "vague" and "confusing"?)

<grin>

Thx,
--don